Of course. But 99.99% of "greens" are technically illiterate (and probably politically illiterate, too), and don't understand that all fluorocarbons are NOT "ozone layer unfriendly", just a select few.
But the real point is that in order to trace the movement of the oil/gas leaks, one needs a "permanent" type of marker species with unique properties not found in nature, and which can be detected in extremely tiny concentrations.
I can't think of anything else that "fits the bill" as well the fluorocarbons. Other halocarbons won't do, as it turns out that there are natural sources of many of them (chlorine, bromine, and iodine analogs).
I believe you’re talking about different scenarios that those which are upsetting the greenies today about fracking. They’re going around hollering “water pollution right now” about fracking sites... not “water pollution in 3000 years when the slow creep of the residual far underground fluid towards the water table has finished.” Radioiodine would suffice to show that no, the fluid has not leaked into the water table on the way past it on the way down, and no it hasn’t leaked into it as a result of acute backing-up from pressure operations down below. Once the pressure has been relieved, there is no more practical danger of such cross contamination.